Precooler/chiller/reheater heat exchanger for air dryers

ABSTRACT

A heat exchanger comprising a precooler and reheater core adjacent a chiller core, first heat transfer passages extending through both cores through which incoming air passes in a first direction, second heat transfer passages extending through the chiller core through which coolant passes in heat exchange relationship with incoming air and perpendicular to the first direction, and third heat transfer passages extending through the precooler and reheater core through which cooled air from the chiller core passes in heat exchange relationship with the incoming air and perpendicular to the first direction. A manifold contiguous with both cores conducts chilled air from the chiller core to the third set of heat transfer passages. 
     Incoming air is chilled in the chiller core and thereafter exchanges heat with the incoming air in the precooler and reheater core to precool the incoming air to form water droplets and to raise the temperature of the chilled air to a usable temperature. The precooled and moist incoming air exchanges heat with coolant in the chiller core such that the air is chilled to a low temperature condensing water vapor therein. The first heat transfer passages include fins staggered and disposed substantially perpendicular to the flow to create an undulating pattern there along for moisture separation within the precooler and chiller cores. The crossflow arrangement of passages in the cores of the heat exchanger advantageously enables the air leaving the precooler and reheater core to enter the chiller core directly without any intermediate channeling or piping.

CROSS REFERENCE TO A RELATED APPLICATION

This application is a continuation-in-part of copending application Ser.No. 08/866,808 filed May 30, 1997, now U.S. Pat. No. 5,845,505 andentitled "Precooler/Chiller/Reheater Heat Exchanger For Air Dryers".

BACKGROUND OF THE INVENTION

This invention relates to the art of heat transfer, and moreparticularly to a new and improved heat exchanger for use in arefrigerated air dryer.

One area of use of the present invention is in refrigerated air drierswherein warm, moist air such as from the interior of a factory, andwhich typically is compressed, is cooled and dried and then conveyed toa location where it is used.

In any compressed air system, it is important to reduce the watercontent of the compressed air as much as possible before delivering thecompressed air to the points of use. This is accomplished by using airor water cooled aftercoolers, moisture separators, and air dryers. Airdryers are available in many different types, and the present inventionis illustrated with a non-cycling direct expansion refrigerated airdryer wherein the compressor operates continuously. This type of airdryer effectively reduces water content in compressed air by physicallychilling the compressed air directly with a refrigeration circuit andthus reducing the capacity of the compressed air to hold water vapor.The water vapor in the chilled compressed air condenses out to liquiddroplets. This combination of air and water droplets flows to a moistureseparator that mechanically removes the droplets from the air stream.The main components in this type of refrigerated air dryer are therefrigeration system, the moisture separator, and two compressed airheat exchangers.

The first of these heat exchangers is a precooler/reheater. It precoolswarm saturated compressed air from the air compressor aftercooler bytransferring heat to chilled air that is returning from the moistureseparator. This part of the process also has the effect of reheating thechilled air before distribution to the end users. The importance of thisheat exchanger is that it reduces some of the cooling load that therefrigeration system would otherwise have to handle. The refrigerationsystem becomes smaller, requiring less power for thriftier operation.The precooler/reheater heat exchanger sometimes is called an"economizer" because of this benefit. Another benefit offered by thisheat exchanger is that it reheats the chilled air coming from themoisture separator. Reheating the chilled air reduces the chances thatlow ambient conditions can cause condensation in the air line downstreamof the dryer. Reheating also reduces the likelihood of pipelinecondensation or "sweating" that can occur on chilled surfaces in humidconditions.

The second heat exchanger is the air chiller. It takes the precooled airfrom the "economizer" and chills it down to the desired dewpointtemperature by rejecting heat into evaporating refrigerant on the otherside of the heat exchanger. After being chilled, the air enters amoisture separator to remove the condensed water and then the airreturns to the "economizer" for reheating.

In conventional refrigerated air dryers the foregoing heat exchangersappear in a variety of types. Most typical are the shell and tube, tubein tube, and plate type heat exchangers. Shell and tube heat exchangerstend to be heavy and they can be costly. Tube in tube heat exchangersare limited to the lower capacity air dryers. The shell and tube typeand the tube in tube type heat exchangers both share the disadvantagesof not being very compact and they require interconnecting pipingbetween the economizer and the chiller. This adds weight, cost,complexity, and pressure drop to the system. Plate type heat exchangersmade from brazing formed plates together may be compact but they lackflexibility due to tooling requirements. Piping to a brazed plate heatexchanger is difficult because the connection locations are so closetogether that they allow very few options for arranging the connections.Brazed plate heat exchangers generally use copper brazed stainless steelplates in their manufacture. This offers corrosion resistance but itmakes them heavy and more costly.

Attempts in the prior art at building combination heat exchangers forair dryers have been counter current designs. Counter current heatexchangers have greater effectiveness but many designs require some kindof intermediate channeling when used in combinations for refrigeratedair dryers. The result is more compact than two separate heat exchangersbut many of the other disadvantages still remain. Combination heatexchangers made from copper brazed stainless steel plates can be purecounter current designs without any intermediate channeling. However,they still retain many of the disadvantages associated with this type ofheat exchanger.

SUMMARY OF THE INVENTION

The present invention provides a heat exchanger comprising a precoolerand reheater core and a chiller core in juxtaposed relation, a first setof heat transfer passages extending through both of the cores throughwhich incoming air passes serially through both cores in a firstdirection, a second set of heat transfer passages extending through thechiller core in heat exchange relationship with the first set of heattransfer passages and through which coolant passes in heat exchangerelationship with incoming air and in a direction substantiallyperpendicular to the first direction, and a third set of heat transferpassages extending through the precooler and reheater core in heatexchange relationship with the first set of heat transfer passages andthrough which cooled air from the chiller core passes in heat exchangerelationship with the incoming air and in a direction substantiallyperpendicular to the first direction. There is provided conduit meansfor conducting chilled air from the chiller core to the third set ofheat transfer passages. This can be in the form of a manifold contiguouswith the two cores to avoid any external piping.

As a result, incoming air is chilled in the chiller core and chilled airtherefrom exchanges heat with the incoming air in the precooler andreheater core to precool the incoming air where water droplets begin toform and to raise the temperature of the chilled air to a temperaturefor ultimate use. The precooled and moist incoming air exchanges heatwith the coolant in the chiller core with the result that the air ischilled to a low temperature causing water vapor therein to condense towater droplets entrained in the flow of air. The first set of heattransfer passages includes heat transfer structures having finsstaggered and disposed substantially perpendicular to the direction offlow therethrough. This creates an undulating or generally sinusoidalflow pattern along the passages which advantageously results in moistureseparation occurring internally within the chiller core. The flowpattern also causes a reduced velocity flow along the passages. Thecrossflow arrangement of passages in the cores of the heat exchangeradvantageously enables the air leaving the precooler and reheater coreto enter the chiller core directly without any intermediate channelingor piping.

Thus, the precooler/chiller/reheater heat exchanger according to thepresent invention addresses the disadvantages of the prior artapproaches by incorporating the two heat exchanger cores into oneintegral unit. The precooler/chiller/reheater heat exchanger is acombination of two brazed aluminum bar and plate heat exchangers. Theflow paths through each heat exchanger core allow for stacking them intoa very compact package. By employing the crossflow arrangement accordingto the present invention, the air flow can exit the precooler/reheaterand enter directly into the chiller without any intermediate channelingto direct the flow. Crossflow can reduce the temperature effectivenessof the precooler/reheater, but the gains in simplicity, weightreduction, heat transfer rate, and pressure drop reduction offset thatloss as will be described in detail presently.

There are many other advantages offered by the arrangement according tothe present invention. Piping to the connections on the heat exchangeris not difficult at all because of the flexibility available inconnection locations. The precooler/chiller/reheater is a brazed bar andplate core with welded on manifolds. This allows for logical connectionplacement harmonious with the different flow arrangements of variousrefrigerated air dryer designs. The heat transfer matrix within theprecooler/chiller/reheater is an enhanced high resistance, low velocitygeometry. That means greater heat transfer in a smaller package. Lowvelocity means that it is possible to incorporate integral moistureseparation into the precooler/chiller/reheater manifolds. Thus,refrigerated air dryers with a precooler/chiller/reheater and integralmoisture separation are simpler to build and less costly. Finally,aluminum construction offers the promise of lower weight and less costthan other types of air dryer heat exchangers.

The foregoing and additional advantages and characterizing features ofthe present invention will become clearly apparent upon a reading of theensuing detailed description together with the included drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a side elevational view, partly diagrammatic, of a heatexchanger according to the present invention as it would appear in arefrigerated air dryer system;

FIG. 2 is a perspective view, with parts removed, of the cores of theheat exchanger of FIG. 1;

FIG. 3 is an enlarged fragmentary perspective view, with parts removed,of a portion of the chiller core in the heat exchanger of FIG. 2;

FIGS. 4 and 5 are enlarged fragmentary perspective views of a portion ofthe chiller core in the heat exchanger of FIG. 2;

FIG. 6 is a diagrammatic view illustrating one aspect of the operationof the heat exchanger of the present invention;

FIG. 7 is a diagrammatic view illustrating another aspect of theoperation of the heat exchanger of the present invention;

FIGS. 8 and 9 are enlarged fragmentary perspective views of a portion ofthe precooler-reheater core in the heat exchanger of FIG. 2;

FIG. 10 is a graph including temperature profiles for theprecooler-reheater core and the chiller core in the heat exchanger ofthe present invention; and

FIG. 11 is a side elevational view, partly diagrammatic, of a heatexchanger according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 shows a heat exchanger 10 according to the present invention asit would appear in a refrigerated air dryer system for handling ambientair from either interior or exterior locations. Heat exchanger 10includes a precooler-reheater core 12 and a chiller core 14 each ofwhich will be described in detail presently. Warm moist air, for examplefrom the discharge of an air compressor aftercooler, enters core 12 ofheat exchanger 10 through an inlet fitting 16 and a manifold 18.Typically the input air is obtained from a compressor 20 connected tofitting 16 via a conduit designated 22. Coolant or refrigerant from asource 24 is supplied to chiller core 14 via an inlet fitting 26 andmanifold 28. Refrigerant is returned from core 14 via a manifold 30 andoutlet fitting 32 to the source 24. The chilled air exits the core 14into a manifold 36 which is in communication with a chilled air outlet38. Outlet 38 is connected via a conduit 40 to a chilled air inlet 42and associated manifold 44 of the precooler reheater core 12. Air leavescore 12 via a manifold 46 and an outlet 48 which is connected via aconduit 50 to a point of use of the processed air.

The path of air travelling through heat exchanger 10 is indicated by thearrows in FIG. 1. The portion 52 of the path is through a stackedarrangement of heat transfer passages in core 12 in heat exchangerelationship with an alternating stack of heat transfer passages throughwhich the chilled air from core 14 passes in a manner which will bedescribed presently. The portion 54 of the path is through a stackedarrangement of heat transfer passages in chiller core 14 which are in analternating relationship with a series of stacked heat transfer passageswhich convey refrigerant in the direction of arrows 56. Thus, the flowsof air and refrigerant in chiller core 14 are in a cross flow, i.e.substantially perpendicular, relationship. Chilled air leaving core 14is conveyed to core 12 and flows along path portion 60. The chilled airin path portion 60 flows along the stacked arrangement of heat transferpassages in core 12 which are in heat exchange relationship with thealternating stacked arrangement of heat transfer passages through whichthe warm, moist incoming air flows along path portion 52. Thus, theflows of warm, incoming air and chilled air in core 12 are in a crossflow, i.e. substantially perpendicular, relationship. The chilled air inpath portion 60 while in core 12 loses some heat to the warm moist airentering heat exchanger 10. This provides a precooling function toimprove the overall efficiency. This also simultaneously results in theair being reheated for its ultimate use. In particular, the air isreheated to a temperature which is less than that of the warm air ininlet 16, 18 by an amount determined by the water vapor content andtemperature of the air in inlet 16, 18.

FIG. 2 shows the precooler-reheater core 12 and chiller core 14 of heatexchanger 10 in greater detail. The two cores are closed on the oppositesides by spaced apart side walls or panels 70 and 72, and the separation74 between panel sections 70a and 70b indicates the junction between thetwo cores. A plurality of spaced-apart heat transfer passages 78a-78eare included within and extend through both cores 12 and 14 horizontallyas viewed in FIG. 2. Each passage, as will be described in detailpresently, includes a heat transfer structure including a plurality offins located between a pair of parting sheets (not shown in FIG. 2). Thepassages 78a-78e are closed at the bottom of the structure shown in FIG.2 by corresponding bars 80a-80e, each of which extends along the entirelength of each of the core structures 12 and 14. Similarly, passages78a-78e are closed at the top of the structure shown in FIG. 2 bycorresponding bars 82a-82e, each of which likewise extends along theentire length of each of the core structures 12 and 14. The passages78a-78e at the left-hand ends as viewed in FIG. 2 are in fluidcommunication with inlet manifold 18 and inlet fitting 16 (not shown inFIG. 2). The passages 78a-78e extend along the entire dimension of core12 and along the entire dimension of core 14, horizontally as viewed inFIG. 2, whereupon the right-hand ends of passages 78a-78e are in fluidcommunication with outlet manifold 36 and chilled air outlet 38 (notshown in FIG. 2). The fins of the heat transfer structure in each of thepassages 78a-78e are disposed substantially perpendicular to thedirection of flow of air indicated by the arrows in FIG. 2 designatingthe path portions 52 and 54. The fins are in a vertically staggered oroffset arrangement as shown in FIG. 2 so that the flow of air along eachof the passages 78a-78e from left to right as viewed in FIG. 2 is in anundulating or sinusoidal-like path as will be shown and described indetail presently.

Chiller core 14 includes a plurality of spaced apart heat transferpassages 86a-86d which extend vertically as viewed in FIG. 2, whichextend along only the core 14, and are in an alternating or stackedrelationship with the passages 78a-78e as shown in FIG. 2. Each passage,as will be described in detail presently, includes a heat transferstructure comprising a plurality of fins located between a pair ofparting sheets which, in the core 14 of FIG. 2, are the parting sheetsof the adjacent passages 78a-78e. Thus, the passages 86a-86d includingthe heat transfer structures thereof are in heat exchange relationshipwith adjacent passages 78a-78e and the heat transfer structures thereof.The passages 86a-86d are closed at the right-hand end of the structureas shown in FIG. 2 by corresponding bars 88a-88d each of which extendsalong the entire length of the right-hand side of core 14 as shown inFIG. 2. Similarly, passages 86a-86d are closed at the left hand end ofcore 14 as viewed in FIG. 2 by corresponding bars 90a-90d, each of whichlikewise extends along the entire length of the left-hand side of core14. The passages 86a-86d at the lower end as viewed in FIG. 2 are influid communication with inlet manifold 28 and refrigerant inlet 26 (notshown in FIG. 2). The passages 86a-86d extend along the entire dimensionof core 14 between bottom and top as viewed in FIG. 2 and thus areperpendicular to or cross-wise in relation to passages 78a-78e. Thepassages 86a-86d at the upper end as viewed in FIG. 2 are in fluidcommunication with outlet manifold 30 and refrigerant outlet 32 (notshown in FIG. 2). Also, like the heat transfer structures of passages78a-78e, the fins of the heat transfer structures in passages 86a-86dare disposed substantially perpendicular to the direction of flow ofrefrigerant which flow path is indicated by the arrows 56 in FIG. 2. Thefins are in a horizontally staggered or offset arrangement as viewed inFIG. 2 so that the flow of refrigerant through each of the passages86a-86d from bottom to top as viewed in FIG. 2 is in an undulating orsinusoidal path as will be described in further detail presently.

Precooler-reheater core 12 includes a plurality of spaced-apart heattransfer passages 96a-96d which extend along core 12 vertically asviewed in FIG. 2 and are in an alternating or stacked relationship withpassages 78a-78e as shown in FIG. 2. Each passage, as will be describedin detail presently, includes a heat transfer structure including aplurality of fins located between a pair of parting sheets which, in thecore 12 of FIG. 2, are the parting sheets of the passages 78a-78e. Thus,the passages 96a-96d including the heat transfer structures thereof arein heat exchange relationship with adjacent ones of the passages 78a-78eand the heat transfer structures thereof. The passages 96a-96d areclosed at the right hand end of the structure as viewed in FIG. 2 bycorresponding bars 98a-98d each of which extends along the entire lengthof the right-hand side of core 12. Furthermore, the bars 98a-98d of core12 are in adjacent or contacting relation with the bars 90a-90d of core14. Thus, two distinct flow regions, for refrigerant in core 14 andcooled air in core 12, are defined and isolated from each other in thestructure of FIG. 2. Similarly, passages 96a-96d are closed at theleft-hand end of core 12 as viewed in FIG. 2 by corresponding bars100a-110d, each of which likewise extends along the entire length of theleft-hand side of core 12. The passages 96a-96d at the lower end asviewed in FIG. 2 are in fluid communication with inlet manifold 44 andchilled dry air inlet 42 (not shown in FIG. 2). The passages 96a-96dextend along the entire dimension of core 12 between bottom and top asviewed in FIG. 2 and thus are perpendicular to or cross-wise in relationto passages 78a-78e. The passages 96a-96d at the upper end as viewed inFIG. 2 are in fluid communication with outlet manifold 46 and reheaterdry air outlet 48 (not shown in FIG. 2). Unlike the structures ofpassages 78a-78e and 86a-86d, the fins of the heat transfer structuresin each of the passages 96a-96d are disposed substantially parallel tothe direction of flow of the chilled air indicated by the path portionrepresented by arrow 60 in FIG. 2. The flow of chilled air along core12, from bottom to top as viewed in FIG. 2, which takes the longest pathof fluid through the structure of FIG. 2, is in a relatively straightpath from one end of core 12 to the other along path portion 60.

FIG. 3 shows in fragmentary perspective the heat transfer structuregenerally designated 110 of passage 78a, the parting sheet 112 betweenpassages 78a and 86a, and the heat transfer structure generallydesignated 114 of passage 86a. Thus, in the right-hand portion of FIG.3, the structure 110 and parting sheet 112 have been removed to show thestructure 114. It is to be understood that the heat transfer structure110 is identical to the heat transfer structure of each of the passages78b, 78c, 78d and 78e. Similarly, it is to be understood that the heattransfer structure 114 is identical to the heat transfer structure ofeach of the passages 86b, 86c and 86d. In addition, the relationshipbetween heat transfer structures 110 and 114 and the parting sheet 112is the same as the relationship between the heat transfer structures ofpassages 78b, 78c, 78d, 78e and of passages 86b, 86c, 86d and theparting sheets therebetween.

Referring first to the heat transfer structure 110, it includes a seriesof fin structures arranged serially in the direction of fluid flow, theflow direction being horizontally as viewed in FIGS. 2 and 3, three ofwhich fin structures are designated 118, 120 and 122 in FIG. 3. The finstructures 118,120 and 122, in turn, are disposed vertically as viewedin FIGS. 2 and 3. Each fin structure, for example the one designated120, includes a thin, sheet-like, end body member 126 which extendsalong the entire length between the top and bottom of core 14 as viewedin FIG. 2. Member 126 is disposed in a plane parallel to the directionof fluid flow and is located at one end of the lateral dimension of thepassage 78a. An identical end body member (not shown) is located at theopposite end of the lateral dimension of passage 78a and offset slightlyfrom member 126 in the direction of fluid flow, i.e. horizontally asviewed in FIG. 3. A first series of spaced-apart end flanges extend inone direction from body member 126, for example the flanges designated130a, 130b, 130c, 130d, etc. extending in a right hand directionhorizontally as viewed in FIG. 3. The flanges 130 are spaced verticallyas viewed in FIG. 3. A second series of spaced-apart end flanges extendin opposite directions from body 126, for example flanges 132a, 132b,132c, 132d, etc. extending in a left hand direction horizontally asviewed in FIG. 3. The flanges 132 are spaced vertically as viewed inFIG. 3. The flanges 130 of the first series are offset or staggered inrelation to the flanges 132 of the second series. The flanges 130 and132 are thin, sheet-like, disposed in the same plane, and are formedintegral with end body member 126.

The fin structure 120 further comprises a first series 134 of spacedlateral flanges or fins which extend laterally of passage 78a and atsubstantially right angles to corresponding ones of the end flanges 130.Preferably each end flange and lateral flange combination is integrallyformed or bent from the thin sheet metal of which the entire finstructure is formed. Thus, as shown in FIG. 3, the lateral fins orflanges 134a, 134b, 134c, 134d etc. are in spaced relation, verticallyas viewed in FIGS. 2 and 3, in the passage 78a. Each lateral flange orfin 134 terminates at the opposite end of the passage 78a where it joinsthe offset end body member mentioned above (not shown) at the oppositeend of the lateral dimension of passage 78a.

The fin structure 120 further comprises a second series 136 of spacedlateral flanges or fins which extend laterally of passage 78a atsubstantially right angles to body member 126. Preferably each lateralflange 136 of the second series is integrally formed or bent from thethin sheet metal of which the entire heat transfer structure is formed.Thus, as shown in FIG. 3, the lateral fins or flanges 136a, 136b, 136c,136d, etc. are in spaced relation, vertically as viewed in FIGS. 2 and3, in the passage 78a. Each lateral flange or fin terminates at theopposite end of the passage 78a where it joins a corresponding endflange (not shown) which extends from the previously mentioned offsetend body member (not shown) which end flange is similar to end flange132 extending from end body member 126.

The fin structure 120 further comprises a third series 138 of spacedlateral flanges or fins which extend laterally of passage 78a atsubstantially right angles to corresponding ones of the end flanges 132.Preferably end flange and lateral flange combination is integrallyformed or bent from the thin sheet metal of which the entire heattransfer structure is formed. Thus, as shown in FIG. 3, the lateral finsor flanges 138a, 138b, 138c, 138d, etc. are in spaced relation,vertically as viewed in FIGS. 2 and 3, in the passage 78a. Each lateralflange or fin terminates at the opposite end of the passage 78a where itjoins another end body member (not shown) offset from the previouslymentioned end body member in the direction of fluid flow at the oppositeend of the lateral dimension of passage 78a.

The fin structure 120 further comprises a fourth series 140 of spacedlateral flanges or fins which extend laterally of passage 78a atsubstantially right angles to body member 126. Preferably each lateralflange 140 of the fourth series is integrally bent or formed from thethin sheet metal of which the entire heat transfer structure is formed.Thus, the lateral fins or flanges 140a, 140b, 140c, 140d, etc. are inspaced relation, vertically as viewed in FIGS. 2 and 3, in the passage78a. Each lateral fin or flange terminates at the opposite end of thepassage 78a where it joins an end flange (not shown) which extends fromthe other end body member (not shown) previously described.

The fins or lateral flanges 134 of the first series are offset orstaggered in relation to the fins or flanges 138 of the third series,and the fins or flanges 136 of the second series are offset or staggeredin relation to the fins or flanges 140 of the fourth series, the offsetor staggered relation being in a vertical direction as viewed in FIGS. 2and 3. The first and fourth series 134 and 140, respectively, are invertical alignment as viewed in FIGS. 2 and 3, and the second and thirdseries 136 and 138, respectively, are in vertical alignment. Thus, fluidflowing through the fin structure 120 in a direction generallyhorizontally from left to right as viewed in FIGS. 2 and 3 firstencounters the fins or flanges 138 which cause the fluid flow to bediverted slightly upwardly and downwardly and around the flat fins 138,whereupon the fluid flows further along in the open space or regionwithin the end flanges 132 and the corresponding end flanges on theopposite lateral end of passage 78a, whereupon the fluid flow encountersthe fins or flanges 140 and 136 which cause the flow to be divertedslightly upwardly and downwardly and around the flat fins 140 and 136,whereupon the fluid flows further along in the open region or spacewithin the end flanges 130 and the corresponding end flanges on theopposite lateral end of passage 78a, whereupon the fluid flow encountersthe fins or flanges 134 which cause the flow to be diverted slightlyupwardly and downwardly and around the flat fins 134, and then the flowcontinues generally horizontally from left to right as viewed in FIGS. 2and 3. As a result, the pattern or shape of the path of fluid flow isundulating or generally sinusoidal proceeding in a horizontal directionfrom left to right as viewed in FIGS. 2 and 3 and which will bedescribed in further detail presently.

The fin structure 118 is substantially identical to that of structure120 and includes an end body member 146, a series of end flanges 152 and154 and a series of lateral fins or flanges 156 and 158, 160 and 162.Structure 118 is located closely adjacent structure 120 in the directionof fluid flow along passage 78a. The lateral fins or flanges 156 ofstructure 118 are offset and staggered in a vertical direction relativeto the adjacent lateral fins or flanges 138 of structure 120 so as tocontribute further to the undulating or sinusoidal movement of fluidalong the passage 78a. Similarly, the fin structure 122 is substantiallyidentical to structure 120 including end body member 166, end flanges170 and 172 and lateral fins or flanges 176, 178, 180 and 182. Structure122 is located closely adjacent structure 120 in the direction of fluidflow along passage 78a. The lateral fins or flanges 178 of structure 122are offset or staggered in a vertical direction relative to the lateralfins or flanges 134 of structure 120 so as to contribute further to theundulating or sinusoidal movement of fluid along passage 78a.

FIG. 3 thus illustrates in detail three fin structures 118, 120 and 122,it being understood that a large number of such fin structures areincluded within both cores 12 and 14 along the length of each passage78a in a direction from left to right as viewed in FIG. 2. Such anarrangement is repeated in each of the other passages 78b, 78c, 78d, and78e. The fin structures preferably are formed of thin sheet aluminum andare brazed to the parting sheets as previously described. In particular,the end body members and end flanges of each of the fin structures arebrazed to the adjacent parting sheet.

The heat transfer structure 114 of passages 86a-86d is identical to heattransfer structure 110, disposed in coplanar relation with respect tostructure 110 and oriented at an angle of 90° with respect to structure110. Since the flow of fluid, i.e. refrigerant, through passages 86a-86dis at right angles to the flow of fluid through passages 78a-78e, heattransfer structure 114 also causes an undulating or generally sinusoidalfluid flow pattern along passages 86a-86d as will be described in detailpresently.

Heat transfer structure 114 includes a series of fin structures arrangedserially in the direction of fluid flow, i.e. vertically as viewed inFIGS. 2 and 3, three of which fin structures are designated 188,190 and192 in FIG. 3. The fin structures 188, 190 and 192 are disposedhorizontally as viewed in FIGS. 2 and 3. Each fin structure, for examplethe one designated 190, includes a thin, sheet-like end body member 196which extends along the entire width of core 14 horizontally from oneside to the other. Member 196 is disposed in a plane parallel to thedirection of fluid flow and is located at one end of the lateraldimension of the passage 86a. An identical end body member (not shown)is located at the opposite end of the lateral dimension of passage 86aand offset slightly from member 196 in the direction of fluid flow, i.e.vertically as viewed in FIG. 3. A first series of spaced-apart endflanges extends in one direction from body member 196, for example theflanges designated 200a, 200b, 200c, 200d, etc. extending upwardlyvertically as viewed in FIG. 3. The flanges are spaced horizontally asviewed in FIG. 3. A second series of spaced-apart end flanges extend inopposite directions from body 196, for example flanges 202a, 202b, 202c,etc. extending downwardly vertically as viewed in FIG. 3. The flanges202 are spaced horizontally as viewed in FIG. 3. The flanges 200 of thefirst series are offset or staggered in relation to the flanges 202 ofthe second series. The flanges 200 and 202 are thin, sheet-like,disposed in the same plane, and are formed integral with each bodymember 196.

The fin structure 190 further comprises a first series 204 of spacedlateral flanges or fins which extend laterally of passage 86a and atsubstantially right angles to corresponding ones of the end flanges 200.Preferably, each end flange and lateral flange combination is integrallyformed or bent from the thin sheet metal of which the entire finstructure is formed. Thus, as shown in FIG. 3, the lateral fins orflanges 204a, 204b, 204c, 204d, etc. are in spaced relation,horizontally as viewed in FIGS. 2 and 3, in the passage 86a. Eachlateral flange or fin terminates at the opposite end of the passage 86awhere it joins the offset end body member mentioned above (not shown) atthe opposite end of the lateral dimension of the passage 86a.

The fin structure 190 further comprises a second series 206 of spacedlateral flanges or fins which extend laterally of passage 86a atsubstantially right angles to body member 196. Preferably each lateralflange 206 of the second series is integrally formed or bent from thethin sheet metal of which the entire heat transfer structure is formed.Thus, as shown in FIG. 3, the lateral fins or flanges 206a, 206b, 206c,etc. are in spaced relation, horizontally as viewed in FIGS. 2 and 3, inthe passage 86a. Each lateral flange or fin terminates at the oppositeend of the passage 86a where it joins an end flange (not shown) whichextends from the previously mentioned offset end body member (not shown)which end flange is similar to end flange 202 extending from end bodymember 196.

The fin structure 190 further comprises a third series 208 of spacedlateral flanges or fins which extend laterally of passage 86a atsubstantially right angles to corresponding ones of the end flanges 202.Preferably each end flange and lateral flange combination is integrallyformed or bent from the thin sheet metal of which the entire heattransfer structure is formed. Thus, as shown in FIG. 3, the lateral finsor flanges 208a, 208b, 208c, etc. are in spaced relation, horizontallyas viewed in FIGS. 2 and 3, in the passage 86a. Each lateral flange orfin terminates at the opposite end of the passage 86a where it joinsanother end body member (not shown) offset from the previously mentionedend body member in the direction of fluid flow at the opposite end ofthe lateral dimension of passage 86a.

The fin structure 190 further comprises a fourth series 210 of spacedlateral fins or flanges which extend laterally of passage 86a atsubstantially right angles to body member 196. Preferably each lateralflange 210 of the fourth series is integrally formed or bent from thethin sheet metal of which the entire heat transfer structure is formed.Thus, the lateral fins or flanges 210a, 210b, 210c, 210d, etc. are inspaced relation, i.e. horizontally as viewed in FIGS. 2 and 3, in thepassage 86a. Each lateral fin or flange terminates at the opposite endof the passage 86a where it joins an end flange (not shown) whichextends from the other end body member (not shown) previously described.

The fins or lateral flanges 204 of the first series are offset orstaggered in relation to the fins or flanges 208 of the third series,and the fins or flanges 206 of the second series are offset or staggeredin relation to the fins or flanges 210 of the fourth series, the offsetor staggered relation being in a horizontal direction as viewed in FIGS.2 and 3. The first and fourth series 204 and 210, respectively, are inhorizontal alignment as viewed in FIGS. 2 and 3, and the second andthird series 206 and 208, respectively, are in vertical alignment. Thus,fluid, i.e. refrigerant, flowing through the fin structure 190 in adirection generally vertically from bottom to top as viewed in FIGS. 2and 3 first encounters the fins or flanges 208 which cause the fluidflow to be diverted slightly to the left and right and then around theflat fins 208, whereupon the fluid flows further along in the open spaceor region within the end flanges 202 and the corresponding end flangeson the opposite lateral end of passage 86a, whereupon the fluid flowencounters the fins 210 and 206 which cause the flow to be divertedslightly to the left and right and around the flat fins 210 and 206,whereupon the fluid flows along in the open region or space within theend flanges 200 and the corresponding end flanges on the oppositelateral end of passage 86a, whereupon the fluid encounters the fins orflanges 204 which cause the flow to be diverted slightly to the left andright and around the flat fins 204, and then the flow continuesgenerally upwardly vertically as viewed in a vertical direction frombottom to top as viewed in FIGS. 2 and 3. As a result, the pattern orshape of the path of fluid flow is undulating or generally sinusoidalproceeding in a vertical direction from bottom to top as viewed in FIGS.2 and 3 and which will be described in further detail presently.

The fin structure 188 is substantially identical to that of structure190 and includes an end body member 216, a series of end flanges 222 and224 and a series of lateral fins or flanges 226, 228, 230 and 232.Structure 188 is located closely adjacent structure 120 in the directionof fluid flow along passage 86a. The lateral fins or flanges 226 ofstructure 188 are offset and staggered in a horizontal directionrelative to the adjacent lateral fins or flanges 208 of structure 190 soas to contribute further to the undulating or sinusoidal movement offluid along passage 86a. Similarly, the fin structure 192 issubstantially identical to structure 190 including end body member 236,end flanges 240 and 242 and lateral fins or flanges 246, 248, 250 and252. Structure 192 is located closely adjacent structure 190 in thedirection of fluid flow along passage 86a. The lateral fins or flanges248 of structure 192 are offset or staggered in a horizontal directionrelative to the lateral fins or flanges 204 of structure 190 so as tocontribute further to the undulating or sinusoidal movement of fluidalong passage 86a.

FIG. 3 thus illustrates in detail three fin structures 188, 190 and 192,it being understood that a large number of such fin structures areincluded within core 14 along the length of passage 86a in a verticaldirection as viewed in FIG. 2. Such an arrangement is repeated in eachof the other passages 86b, 86c and 86d. The fin structures preferablyare formed of thin sheet aluminum and are brazed to the parting sheetsas previously described. In particular, the end body members and endflanges of each of the fin structures are brazed to the adjacent partingsheet.

The heat transfer structures in passages 78a-78e and in passages86a-86d, illustrated in FIG. 3, all characterized by fins or flangesdisposed in the passages substantially perpendicular to the direction offlow, are designated rotated lanced fin structures. These heat transferstructures are a modification of the conventional offset square finstructures where the fins are disposed parallel to the fluid flow in thepassage containing the structures. The rotated lanced fin structures inthe heat exchanger of the present invention are offset square finstructures wherein the fins are angled or rotated 90 degrees relative tothe fluid flow.

For purposes of further illustration heat transfer structures inpassages 78a-78e and in passages 86a-86d of chiller core 14 also areshown in FIGS. 4 and 5. In particular, the heat transfer structuregenerally designated 256 and 258 in FIG. 4 illustrate the rotated lancedfin structures included in the passages 78a-78e and 86a-86d of chillercore 14. FIG. 5 is a mirror image of FIG. 4 to show the fins which arehidden from view in FIG. 4.

Thus, passages 78a-78e which extend through precooler/reheater core 12and through chiller core 14, as well as passages 86a-86d which extendthrough chiller core 14 in cross-flow relation to passages 78a-78e, allinclude heat transfer structures characterized by fins or flangesdisposed in the passages substantially perpendicular to the direction offluid flow through the passages. The fins or flanges are spaced in afirst direction along the passages in the direction of fluid flow, andthey also are spaced in a second direction substantially normal orperpendicular to the direction of fluid flow. Such spacings allow fluidto flow along through the passages. In addition, adjacent sets of finsor flanges are staggered or offset along the second direction. As aresult, fluid flowing along each passage encounters the flanges or finsand flows against and around them so as to result in an undulating orgenerally sinusoidal flow pattern in the direction of fluid flow alongeach passage.

The foregoing is illustrated diagrammatically in FIG. 6 wherein the finsor flanges 260 represent the flanges 134, 136, 138, 140, 156, 158, 160,162, 176, 178, 180 and 182 in passages 78a-78e or the flanges 204, 206,208, 210, 226, 228, 230, 232, 246, 248, 250 and 252 in passages 86a-86d.The direction of fluid flow through the particular passage isrepresented by arrow 262. The flow paths around the fins or flanges 260are indicated by arrows 264. Thus proceeding from left to right asviewed in FIG. 6, which is the direction of fluid flow through thepassage, the undulating or generally sinusoidal pattern of fluid flowaround the fins or flanges 260 can be seen.

The foregoing arrangement of the fins or flanges together with the lowtemperature in core 14 causes the warm, moist air flowing along passages78a-78e in core 14 to release or condense the water vapor in the air. Inparticular, as the warm, moist air flows along passages 78a-78e throughchiller core 14, the water vapor in the chilled compressed air condensesout to water droplets entrained in the flow of air. The flow impingingon the fins or flanges together with the change in direction of the flowaround the fins or flanges as previously described causes the waterdroplets to separate out from the flow of air. This is illustrated inFIG. 7 which shows fins or flanges 260' identical to those designated260 in FIG. 5 and located in the portions of passages 78a-78e withinchiller core 14. The flow paths of air and entrained water dropletsaround fins or flanges 260' are designated 264' in FIG. 7. Some watercollects in the form of droplets 265 on the upstream surface of the finsor flanges 260' and the remainder of the water is released from the airflow in the form of free droplets 266. Both forms of droplets 265 and266 separated from the air flow fall by gravity to the bottom of core 14where collected water is removed via a drain connection 268 shown inFIG. 1.

Thus another advantage of the heat transfer structure according to thepresent invention, characterized by fins or flanges disposedsubstantially perpendicular to the direction of fluid flow through thepassages, is that moisture separation can be accomplished within theprecooler core 12 and within the chiller core 14. This, in turn, avoidsthe need to provide a separate, external moisture separator. On theother hand, in some situations for example due to certain operationalrequirements, or due to the need to shorten the length of header 36 inthe flow direction, or due to certain code requirements, a separateexternal moisture separator may be provided. In that case it is locatedat an appropriate point along conduit 40, for example as designated 280in FIG. 1. Moisture separator 280 can be any one of various commerciallyavailable moisture separators well-known to those skilled in the art.

As previously described, unlike the heat transfer structures of passages78a-78e and 86a-86d, the heat transfer structures in each of thepassages 96a-96d include fins disposed substantially parallel to thedirection of the flow of chilled air along core 12. The heat transferstructures in passages 96a-96d are conventional offset square finstructures well-known to those skilled in the art so that a detaileddescription thereof is believed to be unnecessary. Since the flow ofchilled air along core 12, from bottom to top as viewed in FIG. 2, isthe longest fluid flow path in the heat exchanger structure of FIG. 2,offset square fin structures are employed in passages 96a-96d, with thefins thereof disposed substantially parallel to the fluid flow, so asnot to impose an excessive pressure drop on the fluid flow.

FIGS. 8 and 9 illustrate briefly the heat transfer structures inpassages 96a-96d of precooler-reheater core 12. In particular, the heattransfer structures generally designated 290 and 292 in FIG. 8illustrate the offset square fin structures included in the passages96a-96d of precooler-reheater core 12. FIG. 9 is a mirror image of FIG.8 to show the fins which are hidden form view in FIG. 8.

The heat exchanger 10 of the present invention operates in the followingmanner. Warm, moist air from compressor/aftercooler 20 flows throughconduit 22 into inlet 16 and then into manifold 18 from which the warmmoist air enters passages 78a-78e. The warm moist air flows alongpassages 78a-78e through precooler-reheater core 12. By means of theheat transfer structures in passages 78a-78e and in passages 96a-96dpreviously described, the warm moist air flowing along passages 78a-78eexchanges heat with the chilled air flowing along passages 96a-96d.Thus, the warm, moist incoming air is precooled as it flows alongpassages 78a-78e in core 12 from left to right as viewed in FIGS. 1 and2. This causes the water vapor to begin condensing to water droplets. Inaddition, the rotated lanced fin heat transfer structures in passages78a-78e convert the flow of warm, moist air into an undulating orgenerally sinusoidal flow pattern which causes a reduction in velocityof the flow.

Refrigerant, typically Freon R-22, flows from source 24 to inlet fitting26 and then to manifold 28 from which it enters passages 86a-86d inchiller core 14. Refrigerant flows along passages 86a-86d from bottom totop of core 14 as viewed in FIGS. 1 and 2 whereupon it enters manifold30 and flows through outlet 32 back to the source 24. The refrigerantrecirculates through this continuous circuit.

The precooled, moist air leaves precooler-reheater core 12 and continuesalong the passages 78a-78e through chiller core 14. By means of the heattransfer structures in passages 78a-78e and in passages 86a-86dpreviously described, the precooled moist air flowing along passages78a-78e exchanges heat with refrigerant flowing along passages 86a-86d.The flows of the precooled, moist air along passages 78a-78e andrefrigerant along passages 86a-86d are in crossflow or orthogonalrelation to each other. Thus, the precooled, moist air is chilled to alow temperature as it flows along passages 78a-78e in core 12 and incore 14 from left to right as viewed in FIGS. 1 and 2. This causes thewater vapor in the chilled compressed air to condense in both cores 12and 14 to water droplets entrained in the flow of air. The rotatedlanced fin heat transfer structures in passages 78a-78e further reducethe velocity of the air as it flows through chiller core 14. The rotatedlanced fin heat transfer structures in passages 78a-78e also causeseparation of the water droplets from the air flow along core 14 asdescribed in connection with FIG. 7 with the result that the water fallsby gravity to the lower portion of core 14 as viewed in FIGS. 1 and 2for removal via drain connection 268.

Chilled, dry air leaves passages 78a-78e of core 14 and flows intomanifold 36 and through chilled air outlet 38 whereupon it flows alongconduit 40 and then through chilled dry air inlet 42 into manifold 44from which it enters passages 96a-96d of precooler-reheater core 12. Thechilled, dry air flows along passages 96a-96d from bottom to top of core12 as viewed in FIGS. 1 and 2. By means of the heat transfer structuresin passages 78a-78e and passages 96a-96d previously described, the warm,moist incoming air flowing along passages 78a-78e in core 12 exchangesheat with the chilled, dry air flowing along passages 96a-96d. The flowsof the warm, moist incoming air along passages 78a-78e and chilled, dryair along passages 86a-86d are in crossflow or orthogonal relation toeach other. As a result, as previously described, the warm, moistincoming air is precooled as it flows along passages 78a-78e in core 12from left to right as viewed in FIGS. 1 and 2. This precooling functionadvantageously reduces some of the cooling load that the chiller core 14otherwise would be required to handle. This, in turn, enables thechiller core 14 to be smaller in size requiring less refrigerationsystem power for more economical and efficient operation. Also, thechilled, dry air is elevated in temperature as it flows along passages96a-96d in core 12 from bottom to top as viewed in FIGS. 1 and 2. Theair temperature is elevated for its ultimate use. Reheating the chilledair also reduces the chances that low ambient temperature conditions cancause condensation in the output air line leading from heat exchanger 10to the location of ultimate use. Reheating the chilled air also reducesthe likelihood of condensation or sweating on the output air line thatcan occur on chilled surfaces in humid conditions.

In the heat exchanger 10 of the present invention, the crossflowarrangement in cores 12 and 14 enables the precooled air in passages78a-78e to exit core 12 and enter chiller core 14 directly without anyintermediate channeling to direct the flow. Avoiding intermediate pipingprovides advantages of simplicity in construction and reduction inweight of the heat exchanger 10. The rotated lanced fin structures inpassages 78a-78e through cores 12 and 14 provide moisture separationwithin the heat exchanger and the resulting advantage of elimination ofan external moisture separator. The undulating or sinusoidal-like flowalong the passages containing the rotated lanced fin structuresincreases the turbulence of the flow along those passages. The increasedturbulence, in turn, increases the heat conductance. From therelationship:

    Q=UA(LMTD)

where Q is capacity, U is conductance, A is area of a heat transferstructure, and LMTD is the temperature driving force for heat transfer,it can be seen that the increased U due to increased turbulence enablesthe lengths of the heat transfer passages to be decreased with aresulting decrease in pressure drop.

By way of example, for an illustrative heat exchanger 10 used in arefrigerated air dryer system of the type shown in FIG. 1 and operatingat a flow rate of 300 cubic feet per minute, the dimensions ofprecooler-reheater core 12 are 9.375 inches vertical height and 3.5inches horizontal width as viewed in FIG. 2 and 6.813 inches in depth,and the dimensions of chiller core 14 are 9.375 inches vertical heightand 2.25 horizontal width as viewed in FIG. 2 and 6.813 inches in depth.The temperature of the moist air entering passages 78 of core 12 is 100°F., and the average temperature of the precooled air leaving core 12 is68.2° F. The pressure of the air entering passages 78 of core 12 is 100psig, and the pressure drop in the passages 78 in core 12 is 0.56 psi.

The average temperature of the precooled air entering passages 78 ofchiller core 14 is 68.2° F., and the average temperature of the chilledair leaving core 14 is 38.8° F. The pressure of the air enteringpassages 78 of core 14 is 99.4 psig, and the pressure drop in thepassages 78 in core 14 is 0.34 psi. The evaporation temperature of theR-22 Freon refrigerant in passages 86 of core 14 is 34.0° F. and thepressure is 60 psig. The temperature of the R-22 refrigerant leavingcore 14 through header 30 is elevated a few degrees to insure that onlygas returns to the refrigerant compressor of source 24. This issuperheating requirement which will be discussed in detail presently.

The temperature of the chilled air entering passages 96 ofprecooler-reheater core 12 is 38.8° F., and the average temperature ofthe air leaving core 12 is 85° F. The pressure of the air enteringpassages 96 of core 12 is 98.1 psig, and the pressure drop in thepassages 96 in core 12 is 0.19 psi.

In the rotated lanced fin structures in passages 78 ofprecooler-reheater core 12, the fins are 0.125 inch in height, and thereare eight fins per inch along each passage 78. The fins are of aluminumhaving a thickness of 0.006 inch. The number of the passages 78 in theillustrative heat exchanger is 23. The rotated lanced fin structure inpassages 86 of chiller core 14 are of aluminum 0.125 inch in height and0.006 inch thick. There are eight fins per inch in the passages 86 whichtotal 22 in number of passages. In the offset square fin structures inpassages 96 of core 12, the fins are 0.125 inch in height, and there areeight fins per inch along each passage. The fins are of aluminum havinga thickness of 0.006 inch. The number of the passages 96 in theillustrative heat exchanger is 22. The parting sheets separating thevarious passages are of brazed aluminum having a thickness of 0.024inch.

As previously described, the superheating requirement necessitateselevating the temperature of refrigerant leaving passages 86a-86d ofcore 14 so that only gas and no liquid is returned to the refrigerantcompressor. Otherwise, any liquid returned to the compressor coulddamage it. The crossflow arrangement of passages 86a-86d and passages78a-78d according to the present invention aide in meeting thissuperheating requirement. This can be seen from considering thetemperature profiles of cores 12 and 14 represented schematically at 300and 302 in FIG. 10. The left-hand end of profile 300 is moist airentering passages 78 of core 12 at 100° F. The right-hand end of profile300 shows the temperature range of precooled air in passages 78a-78eleaving core 12 from about 50° F. at the bottom of core 12 in thevicinity of the chilled air entering passages 96 at 38.8° F., to about90° F. at the top of core 12. The average temperature of 68.2° F. ofprecooled air leaving core 12 is indicated on profile 300.

The lower end of profile 302 is R-22 refrigerant entering passages86a-86d of core 14 and the regions of vapor plus liquid and vapor withincore 14 are shown. The right-hand end of profile 302 shows thetemperature range of chilled air leaving passages 78a-78e of core 14from 35° F. at the bottom of core 14 in the vicinity of incomingrefrigerant to 43° F. near the top of core 14. The average temperatureof 38.8° F. of chilled air leaving core 14 is indicated on profile 302.

What is important to note is from considering the top regions of bothprofiles 300 and 302, the 90° F. air leaving core 12 in the upper regionenters the upper region of core 14 to superheat the refrigerant leavingthe upper region of core 14 before it enters header 30 for return to therefrigerant compressor. In particular, the 90° F. air in passages78a-78e leaving the upper end of core 12 and entering the upper end ofcore 14 as viewed in FIG. 2 exchanges heat with the 43° F. refrigerantin passages 86a-86d in the upper end of core 14. This is a result of thecrossflow or orthogonal relationship between passages 78 and 86. Theforegoing heat exchange provides the superheating to elevate thetemperature of refrigerant leaving core 14 to 45° F. as indicated onprofile 302 so as to insure that only gas returns to the refrigerantcompressor.

Thus, in the crossflow arrangement of passages 78 and 86 according tothe present invention, superheating of refrigerant is carried out at the90° F. temperature of the upper portion of core 12 and its temperatureprofile rather than at the 68.2° F. average temperature of precooled airleaving core 12. Because superheating is carried out at the higher 90°F. temperature in the crossflow arrangement of the present invention,less surface area is needed for the superheating because of the highertemperature driving force. This is in contrast to prior art counterflowarrangements which must carry out superheating of refrigerant at therelatively lower average temperature of air leaving theprecooler/reheater core, i.e. at 68.2° F. The prior art counterflowarrangements accordingly need a relatively larger surface area to carryout the superheating because of the relatively lower temperature drivingforce.

FIG. 11 illustrates a heat exchanger 10' according to another embodimentof the present invention. In FIG. 11 components similar to those of theembodiment of FIGS. 1-10 are identified by the same reference numeralsprovided with a prime designation. Thus, heat exchanger 10' includesprecooler/reheater core 12' and chiller core 14' having structuresidentical to those of cores 12 and 14, respectively. Heat exchanger 10'is shown in FIG. 11 as if would appear in a refrigerated air dryersystem for handling ambient air from either interior or exteriorlocations. As in the embodiment of FIG. 1, warm moist air from thedischarge of an air compressor aftercooler 20' enters core 12' of heatexchanger 10' through an inlet fitting 16' and a manifold 18'. Coolantor refrigerant from a source 24' including a compressor is supplied tochiller core 14' via a line 310, inlet fitting 312 and manifold 314.Refrigerant is returned from core 14' via a manifold 316, outlet fitting318 and line 320.

In accordance with this embodiment of the present invention, chilled airleaving chiller core 14' is conducted to precooler/reheater core 12' bymanifold means generally designated 330 in FIG. 11 having a firstsection 332 contiguous with chiller core 14' and a second section 334contiguous with both chiller core 14' and precooler/reheater core 12'.In the arrangement shown, the sections 332 and 334 are disposed atsubstantially right angles to each other. The first section 332 ofmanifold means 330 is in fluid communication with the previouslydescribed set of heat transfer passages 78 (not shown in FIG. 11) ofchiller core 14' along substantially the entire vertical length ofchiller core 14' as viewed in FIG. 11. The second section 334 ofmanifold means 330 has an outlet in fluid communication with thepreviously described set of heat transfer passages 96 (not shown in FIG.11) of precooler/reheater core 12' and at the upper end of core 12' asviewed in FIG. 11. Heat exchanger 10' is oriented so that manifoldsection 332 is disposed generally vertically and manifold section 334 isdisposed generally horizontally and is located above the cores 12' and14'.

There is provided moisture separation means in the form of a demistermesh pad 340 in manifold section 332, preferably extending along thejunction between the passages of core 14' and the interior of manifoldsection 332. A condensate drain 342 at the lower end of manifold section332 as viewed in FIG. 11 serves to remove separated moisture.

Air leaves precooler and reheater core 12' via a manifold 46' and anoutlet 48' which is connected by a conduit (not shown) to a location ofuse of the processed air.

The path of air travelling through heat exchanger 10 is indicated by thearrows in FIG. 11. The portion 350 of the path is through the stackedarrangement of heat transfer passages in core 12' in heat exchangerelationship with the alternating stack of heat transfer passagesthrough which the chilled air from core 14' passes in a manner similarto that of the embodiment of FIGS. 1-10. The portion 352 of the path isthrough the stacked arrangement of heat transfer of heat transferpassages in chiller core 14' which are in the alternating relationshipwith the series of stacked heat transfer passages which conveyrefrigerant in the direction of arrows 354, likewise in a manner similarto that of the embodiment of FIGS. 1-10. Thus, the flows of air andrefrigerant in chiller core 14' are in a cross flow, i.e., substantiallyperpendicular, relationship as in the embodiment of FIGS. 1-10. Chilledair leaving core 14' is conveyed to core 12' by manifold means 330 andflows along path portion 356. The chilled air from manifold section 334flows in the direction of arrows 358 along the stacked arrangement ofheat transfer passages in core 12' which are in heat exchangerelationship with the alternating stacked arrangement of heat transferpassages through which the warm, moist incoming air flows along pathportion 350. Thus, the flows of warm, incoming air and chilled air incore 12' are in a cross flow, i.e., substantially perpendicular,relationship as in the embodiment of FIGS. 1-10. The chilled air in pathportion 358 while in core 12' loses some heat to the warm moist airentering heat exchanger 10'. As in the embodiment of FIGS. 1-10, thisprovides a precooling function to improve the overall efficiency. Thisalso simultaneously results in the air being reheated for its ultimateuse. In particular, the air is reheated to a temperature which is lessthan that of the warm air in inlet 16', 18' by an amount determined bythe water vapor content and temperature of the air in inlet 16', 18'.

The heat exchanger 10' according to this embodiment of the presentinvention takes advantage of the low exit face air velocity from thechiller core 14' to incorporate integral separation. At normal operatingconditions, much of the droplet separation occurs in the heat transfermatrix of cores 12' and 14'. The stainless steel wire mesh pad 340mounted flush with the air side exit face of the chiller core 14'removes any remaining droplets suspended in the air flow. The condensatedrain 342 mounted at the bottom of the chilled air manifold section 332removes the separated moisture. The dry chilled air returns to thereheater through the inverted "L" shaped wrap around manifold 330 thatcompletely eliminates any need for external piping between the chiller14' and the reheater 12'. Lengthening the precooler/reheater core 12',in a vertical direction as viewed in FIG. 11, so the reheater entranceis flush with the top of the refrigerant outlet manifold 316 ensures astraight return path in the tope leg 334 of the air return manifold 330to facilitate manufacturing.

This flow arrangement reverses the flow direction of the reheat air,i.e., the direction of arrows 358 in FIG. 11, as compared to the flowdirection in the embodiment of FIGS. 1-10, i.e., arrows 60 in FIG. 1. Byentering the reheater 12' from the top as viewed in FIG. 11, there isless temperature difference to aid in superheating the refrigerant. But,the greater temperature difference at the other end of the unit causesmore heat transfer at that end and offsets the loss. Tests reveal thatthis flow arrangement is very effective at achieving the dryingobjectives while at the same time providing the necessary superheatingof the refrigerant. By way of example, in an illustrative heat exchanger10', demister mesh pad is a mist eliminator available from ACSIndustries Separations Technology of Houston, Tex. under the designationStyle 4BA.

It is therefore apparent that the present invention accomplishes itsintended objective. While an embodiment of the present invention hasbeen described in detail, that is for the purpose of illustration, notlimitation.

What is claimed is:
 1. A heat exchanger comprising:a. a precooler andreheater core and a chiller core in adjacent relation; b. a first set ofheat transfer passages extending through both of said cores throughwhich incoming air passes serially through both cores in a firstdirection; c. said first set of heat transfer passages including heattransfer structures having fins disposed to influence the flow throughsaid passages; d. a second set of heat transfer passages extendingthrough said chiller core in heat exchange relationship with said firstset of heat transfer passages and through which coolant passes in heatexchange relationship with incoming air and said second set of heattransfer passages including heat transfer structures therein; e. a thirdset of heat transfer passages extending through said precooler andreheater core in heat exchange relationship with said first set of heattransfer passages and through which cooled air from said chiller corepasses in heat exchange relationship with the incoming air and saidthird set of heat transfer passages including heat transfer structurestherein; f. manifold means for conducting chilled air from said chillercore to said third set of heat transfer passages and having a firstsection contiguous with said chiller core and a second sectioncontiguous with both said chiller core and said precooler and reheatercore; g. said fins in said first set of heat transfer passages causingthe incoming air to flow in an undulating pattern along said first setof heat transfer passages which separates moisture from the incoming airas it flows along said first set of heat transfer passages in saidchiller core; and h. said second section of said manifold means beingisolated from moisture separated from said incoming air.
 2. A heatexchanger according to claim 1, wherein said first and second sectionsof said manifold means are disposed at substantially right angles toeach other.
 3. A heat exchanger according to claim 1, wherein said firstsection of said manifold means is in fluid communication with said firstset of heat transfer passages in said chiller core along substantiallythe entire length of said first section and wherein said second sectionof said manifold means has an outlet in fluid communication with saidthird set of heat transfer passages is said precooler and reheater core.4. A heat exchanger according to claim 1, further including moistureseparation means in said first section of said manifold means.
 5. A heatexchanger according to claim 1, wherein said first section of saidmanifold means includes means for removing moisture separated from theincoming air.
 6. A heat exchanger according to claim 1, wherein saidheat transfer structures in said second set of heat transfer passageshave fins in staggered relation to each other and disposed substantiallyperpendicular to the direction of flow through said passages.
 7. A heatexchanger according to claim 1, wherein said heat transfer structures insaid third set of heat transfer passages have fins disposedsubstantially parallel to the direction of flow through said passages.8. A heat exchanger according to claim 7, wherein said heat transferstructures in said third set of heat transfer passages comprise offsetsquare fins.
 9. A heat exchanger according to claim 1, in combinationwith a refrigerated air dryer system.
 10. A heat exchanger according toclaim 1, further including:a. a source of coolant including acompressor; b. means for conducting coolant from said source to saidsecond set of heat transfer passages in a direction toward one end ofsaid chiller core; c. means for returning coolant to said source fromsaid second set of passages in a direction away from another end of saidchiller core; d. the air passing through said first set of heat transferpassages through said chiller core having a temperature profile suchthat the maximum temperature is near said another end of said chillercore; and e. so that the air passing through said first set of heattransfer passages near said another end of said chiller core and at saidmaximum temperature is utilized to superheat coolant returning to saidsource.
 11. A method for precooling, chilling and reheating warm, moistcompressed air in a refrigerated air dryer system comprising:a.providing a heat exchanger comprising a precooler and reheater core andchiller core in adjacent physical relation; b. passing warm, moistcompressed incoming air through said precooler and reheater core toprecool the incoming air; c. passing the precooled incoming air fromsaid precooler and reheater core into and through said chiller core; d.passing coolant through said chiller core to heat exchange relationshipwith the incoming air to chill the incoming air; e. said step of passingthe precooled incoming air through said chiller core including causingan undulating flow pattern in the incoming air flowing through saidprecooler and reheater core and chiller core to increase turbulence andreduce velocity of the incoming air flowing through said precooler andreheater core and separate moisture from the incoming air while in saidchiller core; f. conducting chilled, dry air from said chiller core tosaid precooler and reheater core in a manner preventing introduction ofseparated moisture to said precooler and reheater core by directing saidchilled, dry air exiting from said chiller core initially in a directionopposite the force of gravity so that separated moisture flows in adirection opposite that of said air exiting said precooler and reheatercore; g. passing the chilled, dry air through said precooler andreheater core in heat exchange relationship with the chilled, dry air toprovide said precooling of the incoming air and to elevate thetemperature of the chilled, dry air to provide output air at atemperature for use; and h. conducting output air from said precoolerand reheater core to a location of use.
 12. A method according to claim11, further including withdrawing from said chiller core the moistureseparated from the incoming air.
 13. A method according to claim 11further including:a. providing a source of coolant including acompressor; b. passing coolant from said source toward one end of saidchiller core through said chiller core in crossflow relation to saidincoming air and in heat exchange relationship therewith to chill theincoming air and returning coolant away from another end of said secondcore to said source; c. the air passing through said chiller core havinga temperature profile such that the maximum temperature is near saidanother end of said chiller core; and d. utilizing the air passingthrough said chiller core near said another end of said chiller core andat said maximum temperature to superheat coolant returning from saidanother end of said chiller core to said source.
 14. A heat exchangercomprising:a. a precooler and reheater core and a chiller core inadjacent relation; b. a first set of heat transfer passages extendingthrough both of said cores through which incoming air passes seriallythrough both cores in a first direction; c. said first set of heattransfer passages including heat transfer structures having finsdisposed to influence the flow through said passages; d. a second set ofheat transfer passages extending through said chiller core in heatexchange relationship with said first set of heat transfer passages andthrough which coolant passes in heat exchange relationship with incomingair and said second set of heat transfer passages including heattransfer structures therein; e. a third set of heat transfer passagesextending through said precooler and reheater core in heat exchangerelationship with said first set of heat transfer passages and throughwhich cooled air from said chiller core passes in heat exchangerelationship with the incoming air and said third set of heat transferpassages including heat transfer structures therein; f. manifold meansfor conducting chilled air from said chiller core to said third set ofheat transfer passages and having a first section contiguous with saidchiller core and a second section contiguous with both said chiller coreand said precooler and reheater core; g. said fins in said first set ofheat transfer passages causing the incoming air to flow in an undulatingpattern along said first set of heat transfer passages which separatesmoisture from the incoming air as it flows along said first set of heattransfer passages in said chiller core; h. said second section of saidmanifold means being isolated from moisture separated from said incomingair; and i. said precooler and reheater core and said chiller core beingorientated so that said first section of said manifold means extendsgenerally vertically and said second section of said manifold meansextends generally horizontally.
 15. A heat exchanger comprising:a. aprecooler and reheater core and a chiller core in adjacent relation; b.a first set of heat transfer passages extending through both of saidcores through which incoming air passes serially through both cores in afirst direction; c. said first set of heat transfer passages includingheat transfer structures having fins disposed to influence the flowthrough said passages; d. a second set of heat transfer passagesextending through said chiller core in heat exchange relationship withsaid first set of heat transfer passages and through which coolantpasses in heat exchange relationship with incoming air and said secondset of heat transfer passages including heat transfer structurestherein; e. a third set of heat transfer passages extending through saidprecooler and reheater core in heat exchange relationship with saidfirst set of heat transfer passages and through which cooled air fromsaid chiller core passes in heat exchange relationship with the incomingair and said third set of heat transfer passages including heat transferstructures therein; f. manifold means for conducting chilled air fromsaid chiller core to said third set of heat transfer passages and havinga first section contiguous with said chiller core and a second sectioncontiguous with both said chiller core and said precooler and reheatercore; g. said fins in said first set of heat transfer passages causingthe incoming air to flow in an undulating pattern along said first setof heat transfer passages which separates moisture from the incoming airas it flows along said first set of heat transfer passages in saidchiller core; h. said second section of said manifold means beingisolated from moisture separated from said incoming air; and i. saidheat transfer structures in said first set of heat transfer passagescomprising rotated lanced fins.
 16. A heat exchanger comprising:a. aprecooler and reheater core and a chiller core in adjacent relation; b.a first set of heat transfer passages extending through both of saidcores through which incoming air passes serially through both cores in afirst direction; c. said first set of heat transfer passages includingheat transfer structures having fins disposed to influence the flowthrough said passages; d. a second set of heat transfer passagesextending through said chiller core in heat exchange relationship withsaid first set of heat transfer passages and through which coolantpasses in heat exchange relationship with incoming air and said secondset of heat transfer passages including heat transfer structurestherein; e. a third set of heat transfer passages extending through saidprecooler and reheater core in heat exchange relationship with saidfirst set of heat transfer passages and through which cooled air fromsaid chiller core passes in heat exchange relationship with the incomingair and said third set of heat transfer passages including heat transferstructures therein; f. manifold means for conducting chilled air fromsaid chiller core to said third set of heat transfer passages and havinga first section contiguous with said chiller core and a second sectioncontiguous with both said chiller core and said precooler and reheatercore; g. said fins in said first set of heat transfer passages causingthe incoming air to flow in an undulating pattern along said first setof heat transfer passages which separates moisture from the incoming airas it flows along said first set of heat transfer passages in saidchiller core; h. said second section of said manifold means beingisolated from moisture separated from said incoming air; and i. saidheat transfer structures in said second set of heat transfer passageshaving fins in staggered relation to each other and disposedsubstantially perpendicular to the direction of flow through saidpassages, said heat transfer structures in said second set of heattransfer passages comprising rotated lanced fins.
 17. A method forprecooling, chilling and reheating warm, moist compressed air in arefrigerated air dryer system comprising:a. providing a heat exchangercomprising a precooler and reheater core and chiller core in adjacentphysical relation; b. passing warm, moist compressed incoming airthrough said precooler and reheater core to precool the incoming air; c.passing the precooled incoming air from said precooler and reheater coreinto and through said chiller core; d. passing coolant through saidchiller core to heat exchange relationship with the incoming air tochill the incoming air; e. said step of passing the precooled incomingair through said chiller core including causing an undulating flowpattern in the incoming air flowing through said precooler and reheatercore and chiller core to increase turbulence and reduce velocity of theincoming air flowing through said precooler and reheater core andseparate moisture from the incoming air while in said chiller core; f.conducting chilled, dry air from said chiller core to said precooler andreheater core in a manner preventing introduction of separated moistureto said precooler and reheater core; g. passing the chilled, dry airthrough said precooler and reheater core in heat exchange relationshipwith the chilled, dry air to provide said precooling of the incoming airand to elevate the temperature of the chilled, dry air to provide outputair at a temperature for use; h. conducting output air from saidprecooler and reheater core to a location of use; and i. said step ofconducting chilled dry air from said chiller core to said precooler andreheater core including conducting the air along a first path in agenerally upward direction and then along a second path in a generallyhorizontal direction.